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Actuators for autonomous microrobots
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents actuators used in autonomous microsystems. Characteristic for all actuators presented is the low drive voltage and the low power consumption. Different motion mechanisms have been studied and applied in various locomotion modules for microrobots.

High resolution movement of a monolithic piezoceramic PZT rotational arm module, using a quasi-static motion mechanism, was demonstrated in a 10x10x20 mm3 autonomous robot. The rotational arm comprises multilayer PZT bimorphs and is fabricated by a wet-building technology. The multilayer approach enables operation of the modules at the low drive voltages provided by the robot electronics. In addition a locomotion module has been designed and fabricated based on the above principles.

A three-legged locomotion module with piezoceramic unimorphs, moving by tapping the legs against the floor, has been investigated. Characteristics such as low power consumption, high velocities, low drive voltages and a high weight carrying capability were demonstrated using a resonant motion mechanism.

Highly miniaturized three-legged locomotion modules were developed for a 3x3x3 mm3 autonomous microrobot. The modules comprise a multilayer structure of the electroactive copolymer P(VDF-TrFE) on a flexible printed circuit board (FPC) substrate. A novel multilayer fabrication process suitable for mass production was used. It is based on sequential deposition of spun cast copolymer with evaporated aluminum electrodes. Reactive ion etching is used to microstructure the copolymer and the FPC. The mechanical deformability of the FPC is exploited when folding the 2D FPC-multilayer assembly into 3D locomotion modules. Locomotion was demonstrated by moving a glass slider corresponding to the robot weight.

A modular building technology for microsystems is presented. It uses surface mounting technology and conductive adhesives to assemble modules on a double-sided FPC. Complex geometries were achieved by subsequent folding the FPC. The feasibility of the technology was demonstrated by assembly of the 3x3x3 mm3 autonomous microrobots.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2008. , p. 52
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 431
Keywords [en]
Engineering physics, Locomotion, Microrobot, PZT, P(VDF-TrFE), Autonomous, Multilayer, Actuator
Keywords [sv]
Teknisk fysik
Identifiers
URN: urn:nbn:se:uu:diva-8720ISBN: 978-91-554-7196-5 (print)OAI: oai:DiVA.org:uu-8720DiVA, id: diva2:172023
Public defence
2008-05-23, Siegbahnsalen, Ångströmslaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2008-04-29 Created: 2008-04-29 Last updated: 2009-09-21Bibliographically approved
List of papers
1. Piezoelectric drive platform for cm3-sized autonomous robot,
Open this publication in new window or tab >>Piezoelectric drive platform for cm3-sized autonomous robot,
2004 In: ACTUATOR 2004, 9th international Conference on New Actuators, 14-16 June 2004, Bremen, Germany, p. 106-109Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-97190 (URN)
Available from: 2008-04-29 Created: 2008-04-29Bibliographically approved
2. A piezoelectric disc-shaped motor using a quasi-static walking mechanism
Open this publication in new window or tab >>A piezoelectric disc-shaped motor using a quasi-static walking mechanism
2005 In: J. Micromech. Microeng., ISSN 0960-1317, Vol. 15, p. 2230-2234Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-97191 (URN)
Available from: 2008-04-29 Created: 2008-04-29Bibliographically approved
3. Monolithic fabrication of multilayer P(VDF-TrFE) cantilevers
Open this publication in new window or tab >>Monolithic fabrication of multilayer P(VDF-TrFE) cantilevers
2008 (English)In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 144, no 2, p. 314-320Article in journal (Refereed) Published
Abstract [en]

When operating a piezoelectric actuator the use of multilayers has for a long time proven to be a good solution to maintain a high electric field at a reduced applied voltage. The piezoelectric copolymer polyvinylidene-trifluoroethylene P(VDF-TrFE) has rather low piezoelectric constant compared to piezoceramics but it can withstand much higher electric fields. As the copolymer can be spin coated the individual layer thickness of the multilayer can easily be reduced to a few m and rather large strains can be achieved at a moderate voltage. Here a monolithic fabrication technique for producing P(VDF-TrFE) actuators, without any lamination or adhesive layers, is presented. To fabricate the multilayer successive spin coating of the piezoelectric polymer polyvinylidene-trifluoroethylene P(VDF-TrFE) and electrode evaporation on a substrate was performed. Four different substrate materials were coated with a multilayer stack of 6 active P(VDF-TrFE) layers and 7 aluminum electrodes. The monolithic multilayer structures with patterned electrodes were diced by a cutting saw to produce unimorph cantilevers. No delamination or dissolution could be observed between adjacent copolymer layers. The cantilevers were evaluated in terms of static and resonant deflection and the Q-factor was estimated from the frequency spectra. A discussion regarding the influence of the Q-factor on the fabrication process tolerance is given. The different substrate materials used was stainless steel, flexible printed circuit board (FPC), polycarbonate and aluminum. The Q-factor varied from 30 for the polycarbonate to 83 for the stainless steel. These results provide guidelines for the material choices of a forthcoming locomotion module to be used in the 3 mm 3 mm 3 mm I-SWARM robots. The FPC substrate showed to have the best compatibility to the fabrication processes and the most suitable Q-value of 42. This together with the high deflections makes the FPC the preferred substrate materials the future actuators for the I-SWARM locomotion module. 2008 Elsevier B.V. All rights reserved.

Keywords
Piezoelectric actuators, Copolymers, Electric fields, Multilayers, Printed circuit boards, Spin coating
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-108492 (URN)10.1016/j.sna.2008.01.004 (DOI)000256896700010 ()09244247 (ISBN)
Available from: 2009-09-20 Created: 2009-09-20 Last updated: 2017-12-13Bibliographically approved
4. A processing technique for unimorph multilayer P(VDF-TrFE) actuators
Open this publication in new window or tab >>A processing technique for unimorph multilayer P(VDF-TrFE) actuators
In: Journal of nano- and micromechatronicsArticle in journal (Refereed) Submitted
Identifiers
urn:nbn:se:uu:diva-97193 (URN)
Available from: 2008-04-29 Created: 2008-04-29Bibliographically approved
5. Gentle dry etching of P(VDF-TrFE) multilayer micro actuator structures by use of an inductive coupled plasma
Open this publication in new window or tab >>Gentle dry etching of P(VDF-TrFE) multilayer micro actuator structures by use of an inductive coupled plasma
2008 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 18, no 1, p. 015007-Article in journal (Refereed) Published
Abstract [en]

To fully utilize the actuator properties of poly(vinylidenefluoride) (P(VDF))-based polymers, the electric field has to be rather high and one way to accomplish this, in particular with low voltage drive signals, is to build multilayered structures. This paper focuses on how to structure poly(vinylidenefluoride-trifluoroethylene) P(VDF-TrFE) by presenting an etch method to create multilayered miniaturized actuators, with intermediate aluminium electrodes. To create inter-connect areas for the multilayer electrodes, a modified Bosch process in an inductive couple plasma (ICP) etcher is used to remove all P(VDF-TrFE) not covered by the electrodes. Since each electrode mask is slightly different from the others, the result is a staircase-like inter-electrode contact area that is connected from above using a conductive adhesive. The developed ICP etch results in high selective etching and a good agreement between theoretical and measured capacitance values. The manufactured cantilevers, consisting of a multilayer on top of a flexible printed circuit (FPC) board, were tested and the resonant stroke was confirmed to agree with expected values. The successful establishment of interlayer connections between the electrodes open up the possibility for batch fabrication of cheap low voltage micro actuators built on a standard substrate used in millions of commercial products. 2008 IOP Publishing Ltd.

Keywords
Multilayers, Actuators, Aluminum, Electric field effects, Electrochemical electrodes, Etching, Inductively coupled plasma, Microfabrication
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-108491 (URN)10.1088/0960-1317/18/1/015007 (DOI)000252965900009 ()09601317 (ISBN)
Available from: 2009-09-20 Created: 2009-09-20 Last updated: 2017-12-13
6. Miniature piezoceramic locomotion unit with resonant drive
Open this publication in new window or tab >>Miniature piezoceramic locomotion unit with resonant drive
Article in journal (Refereed) Submitted
Identifiers
urn:nbn:se:uu:diva-97195 (URN)
Available from: 2008-04-29 Created: 2008-04-29Bibliographically approved
7. Building technology for mass-producible autonomous millimeter sized microrobots
Open this publication in new window or tab >>Building technology for mass-producible autonomous millimeter sized microrobots
Manuscript (Other academic)
Identifiers
urn:nbn:se:uu:diva-97196 (URN)
Available from: 2008-04-29 Created: 2008-04-29 Last updated: 2010-01-13Bibliographically approved

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